Pothole growth

Not the one that nearly got me…

Last night I was almost claimed by a pothole. Only catlike reactions honed by three decades of riding the greasy streets of London saved me from disappearing into the giant maw of a pit that seemed to have appeared almost overnight; it sure was not there the previous evening.

This, of course, is the problem with the new breed of pothole. The old kind, usually small and not very deep, might be remembered now with something approaching fondness, not least because it tended to grow only slowly and after a long gestation. The post-Big Freeze pothole, on the other hand, can and usually does grow from nothing to capable of swallowing an HGV wheel within hours of the first initiating crack appearing in the road surface.

The process is well-understood; where any small crack exists in the road surface prior to the freeze, any water in it freezes, expanding by 10% is it does so. This expansion is particularly bad news for domestic plumbing and Tarmac, bursting pipes in the first instance and breaking up the material that forms a Tarmac road surface in the latter.

The big problem for road surfaces is that the smooth top layer sits on top of compacted rubble of progressively coarser size and, once the ice has cracked the the top layer and can seep into the substrate, it has more room to work in and quickly “uncompacts” the rubble. Heavy road traffic then pounds the now-softened road, creating a dip, smashing into the edges to clear loose stones and grit, making a hole and exposing the dark underbelly of the road surface. 

Bad news for motorised vehicles, this is even more so for cyclists who fail to see a new hole in time to avoid it. However, we can do things car and lorry drivers can’t, such as jump the bike. In fact, this is about the only thing that can be done once it is too late to veer around the hole. It is what I did last night and, although the Mother of all Potholes was just that bit too big to clear even at over 20mph, I got most of the way over and managed a soft landing on the facing slope. Soft enough, anyway, not to flat the back tyre or dent the rim, which is more than can be hoped for in the circumstances.

About the only good news from the whole affair is that local councils are having to take the deterioration of road surfaces seriously and that plenty of new Tarmac is being laid, around south London at least. Maybe that hole will have gone by the time I reach it tonight.

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